Patients are given an injection of a tracer and undergo lymphoscintigraphy 2-3 hours later to identify the sentinel lymph node. Within 24 hours after lymphoscintigraphy, patients undergo wide local excision of the tumor or mastectomy after the sentinel node is removed. If no sentinel node is found or metastasis is found in a nonsentinel node, patients undergo complete axillary lymph node dissection (ALND) regardless of randomization. Sentinel node-negative patients receive no further treatment. Sentinel node-positive patients continue treatment according to randomization.